KR940008958B1 - Absorbent article - Google Patents

Abstract

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Description

Layered absorbent insert with superabsorbent concentration gradient in the Z direction

1 is a perspective view schematically showing a disposable garment according to the present invention.

FIG. 2 is a lateral side view of a disposable garment cut along the section 2-2 of FIG. 1, and schematically shows a superabsorbent concentration gradient composed of superabsorbent particles of non-uniform size.

3 schematically shows a superabsorbent concentration gradient composed of superabsorbent particles composed of superabsorbent particles having a substantially constant particle size.

FIG. 4 schematically illustrates a superabsorbent concentration gradient in which particles of large particle size are predominantly located near the body sidel of the absorbent batt.

5 schematically shows a superabsorbent concentration gradient whose concentration is maximum at the center of the absorbent bat.

FIG. 6 schematically shows a superabsorbent concentration gradient with minimal concentration located between the body side and the outer side of the absorbent bat.

Figure 7 shows a graph illustrating an example of a schematic concentration gradient throughout the thickness dimension of the absorbent article of the present invention.

FIG. 8 shows a graph illustrating a superabsorbent concentration gradient where the concentration is minimal at the location between the body side and the lateral side of the absorbent bat.

FIG. 9 is a cross-sectional side view of a disposable garment of the prior art in which the superabsorbent particles are distributed almost uniformly in an absorbent bat.

FIG. 10 shows a graph illustrating the distribution of superabsorbent particles in a prior art garment defined in a band of superabsorbent particles that are almost uniformly distributed in the absorbent bat or that are in a substantially discontinuous layer.

FIG. 11 schematically shows the concentration gradient of the superabsorbent starting from the discontinuous distance away from the body side of the absorbent layer and ending at the discontinuous distance away from the outer side of the absorbent layer.

* Explanation of symbols for main parts of the drawings

4: diaper 6: inner liner

8: backsheet 9: absorbent crepe cotton

10: batt 11: tissue sheet

12: end edge 14: side portion

16: bottom 18: waistband portion

20 stretch elastic means 22 pressurized tape

24: superabsorbent particles 26: thickness

28: width 30: vertical length

32: Z direction

The present invention relates to absorbent products. More specifically, the present invention relates to an absorbent article containing superabsorbent particles dispersed in the absorbent article.

Disposable products, such as diapers, sanitary napkins, incontinence garments, bandages, and the like, use pads or batts of absorbent material that absorb and retain liquids, such as body secretions. Enormous efforts have been made to increase the amount of secretion that can be retained by the absorbent pad. Increasing the absorbency of the pad can advantageously reduce the physical size of the pad, such as thickness.

Various types of absorbent pads have incorporated superabsorbent materials such as superabsorbent polymers to increase the secretory retention capacity of the pads. In certain designs, superabsorbent materials have been selectively placed in specific discrete zones of the pad. For example, US Pat. No. 3,888,257 to June 10, 1975 by R. Cook and its co-inventors describes a disposable absorbent product comprising a matrix of fibrous wood pulp. Hydrocolloid polymer particles are located in three dimensions dispersed in the central zone or strip of the fibrous matrix. D. June 8, 1982 United States Patent No. 4,333,462 to D. Holtman and its co-inventors describes an absorbent structure comprising an absorbent batt containing two reservoirs. The first reservoir is opened towards the cover of the product, and the second reservoir is located below the first reservoir and contains superabsorbent particles. R., May 3, 1983. US Patent No. 4,381,783 to R. Elias describes an absorbent article comprising an absorbent layer having at least one discontinuous inner pocket. The pocket contains a uniform mixture of discontinuous superabsorbent particles and discontinuous introfying particles. P. May 3, 1983. U.S. Patent No. 4,381,782 to P. Mazurak and co-inventors discloses a superabsorbent, low density fibrous structure, such as a web or batt, comprising a mixture of powdered or microcrystalline hydrogel formulations and a filler treated with a surfactant. It is described.

The hydrogel formulation is located in a transverse band or strip extending transverse to the width of the absorbent bat. Dated June 8, 1982. U.S. Patent No. 4,333,465 to G. Wieqner describes a sanitary napkin comprising an absorbent hydrophilic fiber filling material. The internal core of the filler material contains inserts containing superabsorbent polymer therein. British Patent No. 1,406,615, issued September 17, 1975, describes absorbent pads comprising absorbent gelling agents such as cellulose ethers, cellulose esters, and acetyl starch. This gelling agent is located in the selected central area of the pad.

The following patents describe absorbent pads comprising a center layer or center zone of a material that is more absorbent than the rest of the pad. That is, dated February 19, 1929. US Patent No. 1,702,530 to H.Williams, J. January 1, 1963. J.J. US Patent No. 3,073,309 to J.E.J.Mosier and J. February 18, 1964. M. US Patent No. 3,121,427 to J.M.Mosier.

US Patent No. 3,669,103 to B. Harper and its co-inventors, dated June 13, 1972, is suitable for the body containing a dried solid consisting of a slightly crosslinked polymer, ie a water swellable and water insoluble polymer absorbent. Absorbent products constructed with supports are described. Mr. June 20, 1972. C. Harmon, US Patent No. 3,670,731, describes an absorbent dressing comprising a water soluble hydrocolloid composition. The hydrocolloid may be mixed with the fibers of the absorbent pad or may be located in a discontinuous layer along the major surface of the absorbent article.

The absorbent pad includes superabsorbent particles arranged in a strip pattern. For example, K, July 13, 1976. K. Hokanson, US Pat. No. 3,968,798, describes a C layer array of absorbent pads filled with hydrocolloid polymer particles uniformly dispersed in the middle portion. US Pat. No. 4,410,324 describes a disposable diaper having an absorbent pad folded in the middle of a sock end to increase the absorbent at the groin contact area of the diaper. The hydrocolloid material may be located in the strip along the edge of the absorbent pad.

British patent application GB 2,145,661 A describes an absorbent article consisting of at least two discontinuous superabsorbent layers and wicking means. The wicking means extends around and between the superabsorbent layers to assist in the distribution of the liquid.

Conventional absorbent products as described above have not effectively exploited the full potential of superabsorbents. When the superabsorbents absorb the secretions, they typically swell to form a gel structure. This gel structure often prevents the secretion from moving further to the rest of the absorbent structure. As a result, the secretion cannot reach the remaining superabsorbents, and the efficiency of the absorbent product is greatly reduced. There are several techniques for overcoming this "gel disorder" phenomenon. For example, techniques have been used to uniformly distribute the superabsorbent particles in the absorbent pad and to employ a discontinuous wicking mechanism such that the secretion is distributed over the total amount of superabsorbent. However, conventional techniques for reliably distributing secretions and making full use of the total amount of superabsorbent material were not complete and unsatisfactory.

Another drawback of conventional absorbent structures using superabsorbents was the unpleasant, slippery gel-like feel that occurs on the surface of the absorbent structure. This sticky unpleasant touch is particularly acute for absorbent pads bonded to garments such as infant diapers, incontinence garments, and feminine sanitary napkins. Conventional absorbent articles have solved this problem by selectively isolating the superabsorbent at a location remote from the wearer's body contact surface of the product. For example, superabsorbents have been confined to the core portion of the absorbent product and have been confined to the outer layer of the absorbent product away from the wearer's body. However, these techniques have encountered the problem of gel failure. As a result, conventional absorbent articles have not sufficiently solved the gel impairment but also have not sufficiently isolated the gel forming superabsorbent from the body side of the garment wearer.

The present invention provides an improved absorbent article comprising an absorbent layer having a certain length, width and thickness. The superabsorbent particles are distributed in the absorbent layer, and these superabsorbent particles are arranged to form a nearly continuous, non-step-wise layerless concentration gradient through at least a portion of the thickness dimension of the absorbent layer.

In concentration gradients over the thickness of the absorbent layer, the unique arrangement of the superabsorbent reduces the incidence of gel failure and improves the certainty of the secretion distribution over the entire amount of superabsorbent. In addition, increasing the superabsorbent concentration in selected areas of the absorbent layer reduces potential contact of the gel material with the body of the garment wearer. As a result, the product of the present invention provides an absorbent structure that utilizes a certain amount of superabsorbent more effectively and improves the simplicity of the garment.

The present invention will be more fully understood by the following detailed description of the invention and a brief description of the drawings, and further, the advantages thereof will become apparent.

While the following detailed description describes, by way of example, disposable diapers, it will be readily appreciated that the absorbent structure of the present invention may be used in various other types of products, such as sanitary napkins, incontinence garments, bandages, absorbent handkerchiefs, and the like. All such products fall within the scope of the present invention.

Referring to FIG. 1, the disposable diaper 4 comprises a liquid permeable innerliner 6, a liquid impermeable outer surface layer such as a backsheet 8 and an absorbent layer such as the bat 10, wherein the bat is the liner. It is located between and the backsheet. The inner liner and backsheet are larger than the absorbent bat and have an end marginal portion 12 extending beyond the end of the bat 10. The liner and backsheet also have a side marginal portion 14 extending beyond the side of the bat. Typically, the liner 6 and the backsheet 8 are secured to each other along the edges 12 and 14.

The component of the diaper 4 uses conventional materials. The liner 6 may consist of a fairly soft and flexible porous sheet through which the fluid passes, for example a nonwoven web or sheet of polyolefinic fibers such as polypropylene fibers. The liner may also consist of wet strength tissue paper, spunwoven filament sheets, and the like. In addition, the liner may be treated with a surfactant to promote the transfer of secretion.

The backsheet 8 is a liquid impermeable layer and may consist of a thin web or sheet of plastic film such as polyethylene, polypropylene, polyvinyl chloride, or the like. The backsheet can be transparent or embossed or matted to render the surface opaque.

The absorbent bat 10 may be any suitable material and is a cellulosic material, such as an airformed bat of wood pulp fibers, commonly known as “fluff”. The absorbent crepe filling material or tissue sheets 9 and 11 may be positioned between the absorbent bat 10 and the liner 6 and the backsheet 8, respectively.

The liner 6, the backsheet 8 and the absorbent bat 10 are joined together in a suitable manner to form the diaper finished product. These elements may be joined to each other by strips or patterns of hot melt or pressure sensitive adhesive, electrothermal bonding or pattern thermal bonding, strips of double faced, pressure-sensitive adhesive tape, and the like. Particularly effective bonding systems use evenly spaced parallel lines of hot melt adhesive located on the inner surface of the backsheet 8. The absorbent bat is bonded to the backsheet along the bond line portion, and the liner 6 is located within the edges 12 and 14 but along the other portion of the bond line located outside the bat 10 area. Is bonded to.

The diaper 4 generally has an hourglass or I-shape, which includes a narrow bottom 16 near the center of the diaper and a herbaceous portion 18 at each end of the diaper. The stretchable elastic means 20 are coupled at appropriate locations adjacent the absorbent bat 10 and on each side thereof to develop a gathered elastic leg portion that matches the infant's leg. The conventional pressure tape 22 is attached to one belt portion 18. The diaper 4 is made to be suitable for the infant as the inner liner 6 against the skin of the infant. One waistband surrounds a portion of the infant's waist, and the other waistband portion surrounds the rest of the infant's waist. The two waistband portions overlap and are joined by a pressure-sensitive adhesive tape 22 that manipulates the diaper to hold it in place. As shown in FIGS. 1 and 2, the diaper 4, in particular the absorbent bat 10, generally has a longitudinal dimension 30 and a transverse dimension 28 from the side. In addition, the bat 10 has a thickness dimension 26 that extends substantially in the Z direction 32. As shown in FIG. 2, the superabsorbent 24 is disposed in the absorbent layer made of the bat 10. The superabsorbent particles form a superabsorbent of substantially continuous unstepped concentration gradient throughout the thickness fixture of the absorbent layer. As a result, the superabsorbent particles are arranged in a substantially flat structure. Superabsorbents are not limited to any particular level or layer within the thickness of the absorbent bat.

For the purposes of the present invention, the term "superabsorbent" means a material capable of absorbing and retaining body fluid at least about 15 times its own weight under 0.5 psi pressure. Such superabsorbent material is guar gum. Superabsorbents also include polymers such as sodium polypropene acid, starch grafted polypropene acid, polypropene acid amide, and the like.

According to FIG. 3, the absorbent bat 10 has two major surfaces. One major surface is located closest to the liner 6 and is generally referred to as the body contact surface of the bat. The other major surface of the bat 10 is located closest to the backsheet 8 and is generally referred to as the outer surface of the bat 10.

In order to improve the absorbent capacity of the bat 10, the superabsorbent particles 24 are distributed to form a concentration gradient when observing continuous levels within the thickness of the diaper 4 moving along the Z direction. In the specific example shown in FIG. 2, the superabsorbent concentration gradually increases over at least a portion of the thickness dimension of the diaper 4, continuing in order starting from the body side of the bat 10 and ending at the outer side of the bat. It provides a positive gradient when observing physical positions. Superabsorbent particles are substantially evenly distributed across the width of the absorbent layer, as measured at a particular thickness level of the absorbent bat. Superabsorbent particles are also distributed substantially uniformly along the length of the absorbent layer, as measured at a particular thickness level of the absorbent bat.

In a feature of the invention, the superabsorbent concentration on the body side of the bat is less than the average superabsorbent concentration on the bat, and the superabsorbent concentration on the outside of the bat is greater than the average superabsorbent concentration. For example, superabsorbent concentration gradually increases when observing different levels of concentration in the bat taken when moving from the body side to the outer surface.

For the purposes of the present invention, localized superabsorbent concentration is measured by taking slices throughout the absorbent bat along a plane generally perpendicular to the Z direction to expose selected layers within the bat 10. The exposed area ratio of the bat covered with superabsorbent particles is considered as the area percent concentration. Once the area percent concentration is determined, the weight percent concentration can be calculated by assuming spherical particles and raising the area percent concentration to 3/2 square and taking into account the density of the different materials in the slice. The average superabsorbent area concentration in bat 10 is determined by exposing at least three layers in the bat to determine its localized site concentration, and then calculating the average value of these area concentrations. The average weight concentration can be calculated in a similar manner, taking into account the different densities of superabsorbents and conventional absorbents.

The absorbent structure described provides several important advantages. Lower concentrations of superabsorbent particles near the body side of the bat 10 and higher concentrations of particles near the bat outer surface advantageously reduce the movement of the superabsorbent in use. In addition, the concentration gradient of the superabsorbent particles can improve the absorbency. Lower concentrations of superabsorbents on the body side of the bat reduces gel disturbances on the body side. As a result, the secretion flows and leakage of the secretion is reduced, and the use of the entire absorbent structure becomes more complete. Lower concentrations of superabsorbents on the body side of bat 10 may also result in stagnation of a sudden influx of fluid, which may then release them at relatively low rates to areas of the bat with higher superabsorbent concentrations. Acts as.

In the specific example shown in FIG. 2, the superabsorbent particle size in the concentration gradient is essentially irregular. However, the particle size distribution can have a different arrangement. For example, as illustrated in FIG. 3, the superabsorbent concentration gradient may consist of particles of substantially constant particle size.

In another feature of the invention, the superabsorbent particles located near the body side of the bat 10 are, on average, larger in size than the superabsorbent particles located toward the outer side of the bat. In particular, superabsorbent particles located near the body side of bat 10 have an average diameter of less than about 300-1,000 μm. Superabsorbent particles located toward the outer surface of bat 10 have an average diameter of less than about 300 μm. The average particle size at the external tooth between the body side and the lateral side of the bat 10 generally decreases when observing particles moving toward the lateral side at the body side of the bat 10.

In another aspect of the invention, the concentration of superabsorbent is approximately zero relative to the discontinuous distance to bat 10, as measured from the body side of the bat. As a result, the superabsorbent concentration gradient in the Z direction, as described in FIGS. 7 and 11, measured at the bat outer surface starting from a point below the upper body side of the bat 10 and rising from zero, The superabsorbent concentration over the discontinuous distance to the bat 10 may also be zero. As a result, the superabsorbent concentration gradient in the Z direction ends before reaching the outer surface of the bat 10 or returns to zero.

For the purposes of the present invention, the concentration gradient in the positive Z direction is thought to start at the point closest to the body side of the bat 10 where the concentration of superabsorbent is substantially zero, and the body of the bat Gradual increase begins when observing successive layers in bats farther from the flank. Similarly, the superabsorbent concentration in the Z direction is thought to end at the point closest to the outer surface of the batt or the outer surface of the bat 10 whose concentration falls to a substantially zero value.

In particular, in an effective aspect of the invention, the ratio of superabsorbent concentration at which the gradient begins to superabsorbent concentration at which the gradient ends is at least 1: 2 or as measured by percent weight concentration as measured by area percent concentration. At least 1: 3. To enhance the effect, the beginning to end gradient ratio is at least about 1: 5 as measured by area percent concentration or at least about 1:11 when measured by weight percent. More preferably, the concentration gradient from start to end is at least about 1: 10 or at least about 1: 30, as measured by weight percent, as measured by area percent. In another preferred aspect of the present invention, the concentration gradient straight line has a positive slope within the range of about 0.02 to 0.5, preferably 0.03 to 0.4, more preferably about 0.05 to 0.2. The slope of the concentration gradient line is determined by taking the change in delta (Z) at the area percent superabsorbent concentration and dividing by the change in delta (%) at the Z direction thickness of the bat 10 where the change in area percent concentration occurs. do. This calculation is illustrated in FIG.

Relative percent concentration is determined by dividing bat 10 along a plane substantially perpendicular to the Z direction. This exposes the selected surface layer in the bat. The relative area percent concentration is then determined by comparing the amount of area covered with the superabsorbent particles relative to the total exposed area of the bat. The weight percent concentration can then be calculated using the density of the absorbent flup material and the density of the superabsorbent particles.

The area percentage of a particular layer in the bat 10 covered with superabsorbent particles was determined using the following procedure. The selected layer is exposed by cutting, stripping or otherwise removing the underlying bat material. The exposed layer is then clouded using an indicator solution to color and sometimes swell the superabsorbent particles. The indicator solution creates a contrast between the superabsorbent particles and the batt material, and the contrast area is measured with an image analyzer, such as the Cambridge Quantimet 900 Image Analysis System, covered with the superabsorbent particles. Determine the relative percent area.

In the example of the above procedure, the superabsorbent particles contain starch and are turbid with an aqueous solution of potassium iodide (KI ₂ ). The aqueous solution was prepared from a stock solution of 10 g of KI, ₁ g of I ₂ and sufficient water to obtain a liquid solution having a total volume of 100 ml. The actual turbid solution contained 5-10% of the stock solution. The gas chromatography nebulizer was placed at a position of 25.4 to 30.48 cm (10 to 12 inches) from the bat sample, and the sample was turbid for about 5 to 10 seconds until a droplet of 1 to 2 mm in diameter with nuclei formed around the sample. . The aqueous KI ₂ indicator solution swelled the superabsorbent particles and increased their area of application by a factor of about 2. This increase and expansion of the superabsorbent particles increased the sensitivity of the test. Appropriate adjustments were made to the interpretation of the final image analysis to make corrections for particle expansion and to determine the band covered with the dry particles.

5 illustrates one aspect of the invention in which the concentration of superabsorbent in the central nucleus of bat 10 is greater than the concentration at the body side or lateral surface of the bat. For performance improvement, it is about 10 times the superabsorbent concentration at the end of the gradient characteristic of the area percent superabsorbent concentration at the center of the concentration characteristic gradient.

6 and 8 illustrate one aspect of the invention wherein the superabsorbent concentration at the central portion of the bat 10 is less than the concentration of the body side or lateral side of the bat. In the example shown, the superabsorbent area percentage concentration decreases when observing the area concentration in the continuous layer within the bat starting from the body side of the bat 10. Area percent concentration begins to increase after reaching the minimum and provides a positive slope for the concentration gradient. Also, the superabsorbent concentration on the body side of the bat is less than the superabsorbent concentration on the outside of the bat.

For improved performance, the total amount of superabsorbent particles is comprised of 12-15 wt% of the hybrid absorbent bat. Hybrid batts include both conventional and superabsorbents. When a conventional fibrous absorbent consists of wood pulp flutes, the flutes are compacted to a flop density in the range of about 0.13 to 1.18 g / cc.

The amount of superabsorbent that is about 15% or more by weight does not improve the absorbent performance and may actually reduce its performance. Fluff densities up to about 0.13 g / cc result in poor fluid distribution, while flup densities above 0.18 g / cc do not improve the fluid distribution further and have undesirable properties such as hard spots, stiffness, poor fluid intake and Cause poor wearability.

The following examples are given to better understand the present invention. Certain materials, amounts, and other variables described in the examples are illustrative only and are not intended to particularly limit the scope of the present invention.

EXAMPLE

According to the present invention a sample diaper product was constructed having the properties listed in Table 1 below.

TABLE 1

Z direction distribution of superabsorbent

* Approximation by calculation

SAM = Super Absorbent

Sample 1 is preferred. This is because the specimen has a positive superabsorbent concentration gradient throughout the thickness of the bat. Sample 2 is less desirable because it has a relatively high superabsorbent concentration near the bat body side. The preferred amount slope for the concentration gradient begins as a ratio somewhere in the center portion of the bat.

In contrast to diapers constructed in accordance with the invention, conventional diapers have the properties described in Table 2.

Conventional diapers have superabsorbent particles dispersed substantially uniformly throughout the absorbent bat.

TABLE 2

* Approximation by calculation

SAM = superabsorbent

Leak test comparison data are shown in Table 3. These data indicate that absorbent structures with low levels of superabsorbent near the body side of the bat and high levels of superabsorbent near the outer side of the bat are compared with conventional structures with homogeneous superabsorbent dispersion throughout the flup layer. This results in less leakage of urine and less amount of superabsorbent transfer to the inner liner.

TABLE 3

Performance vs. Superabsorbent Z Direction

(a) Distribution ratio based on qualitative analysis

(B) A 250g LKG 50 value means that 50% of the diapers failed before absorption of 250g of secretion during use overnight.

SAM = superabsorbent

BSL = Body Side Liner

As described in detail above, it is obvious that all possible modifications and changes can be made to the present invention within the scope of the appended claims.

Claims (12)

a) an absorbent layer having a certain length, width and thickness, b) superabsorbent particles distributed within the absorbent layer, and c) the superabsorbent is substantially continuous through at least a portion of the absorbent layer thickness. absorbent product comprising the superabsorbent particles arranged to form a step-wise positive concentration gradient. The absorbent article as set forth in claim 1, wherein the superabsorbent particles are substantially uniformly distributed in the transverse direction in the width of the absorbent layer when measured in a specific thickness layer of the absorbent layer. The absorbent article as set forth in claim 1, wherein the superabsorbent particles are substantially uniformly distributed in the longitudinal direction of the absorbent layer when measured at a specific thickness of the absorbent layer. The absorbent article as set forth in claim 1, wherein the superabsorbent concentration gradient gradually increases when the superabsorbent concentration is measured at a distance away from the body side of the absorbent layer. The superabsorbent concentration on the body side of the absorbent layer is less than the average superabsorbent concentration of the absorbent layer, and the superabsorbent concentration on the outer surface of the absorbent layer is larger than the average superabsorbent concentration. Phosphorus absorbent products. The absorbent article as claimed in claim 1, wherein the superabsorbent particles located on the body side of the absorbent layer have a larger average particle size than the superabsorbent particles located on the outer surface of the absorbent layer. The absorbent article of Claim 1, wherein the superabsorbent concentration is substantially zero relative to the discontinuous distance measured from the body side of the absorbent layer to the absorbent layer. The absorbent article as set forth in claim 1, wherein the superabsorbent concentration is substantially zero with respect to the discontinuity measured from the outer surface of the absorbent layer to the absorbent layer. The absorbent article as in claim 1, wherein the superabsorbent concentration is greater than the concentration at the body side and its outer surface at some location through the thickness of the absorbent layer. 10. The method according to any one of claims 7 to 9, characterized in that the superabsorbent particles located near the body side of the absorbent layer are on average larger than the superabsorbent particles located near the outer surface of the absorbent layer. Absorbent products. 11. The absorbent article as in claim 10, wherein the particle size of the superabsorbent particles near the body side of the absorbent layer is about 300 to 1,000 [mu] m. 11. The absorbent article as in claim 10, wherein the particle size of the superabsorbent particles located on the outer surface of the absorbent layer is less than about 300 micrometers.

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